I have the same "sleep but not waking requiring a hard power off to reset" that many others have had. Unfortunately after many failed attempts to try things in this forum the problem still persists. This is making it a pain to use Ubuntu. I seem to remember everything working fine with 9.04. The wheels fell off on 10.04 so that sleep-wake might work 50% of the time.

FYI - All sleep and wake functionality works fine in Windows Vista.

Here is a description of my computer:

Homebuilt desktop
Ubuntu 11.04 Natty
- 2.6.38-8-generic-pae
- Gnome 2.32.1
- Using "Classic" Ubuntu interface
- Same problem with Unity interface
ASUS P5K/EPU Motherboard
- 4 GB RAM
- ACPI 2.0
- No overclocking
Intel Core 2 Duo E8400 3.0 GHz
- No overclocking
Nvidia GeForce 8800 GS
- Same problem with driver 185 (recommended in additional hardware)
- Rolled driver back to 173.14.30
- VBIOS 62.92.1f.00.28
- No overclocking

If anyone can help please give me a clue.

lspci output:

00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 02)
00:01.0 PCI bridge: Intel Corporation 82G33/G31/P35/P31 Express PCI Express Root Port (rev 02)
00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 02)
00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 02)
00:1a.2 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 02)
00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 02)
00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 02)
00:1c.4 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 5 (rev 02)
00:1c.5 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 6 (rev 02)
00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 02)
00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92)
00:1f.0 ISA bridge: Intel Corporation 82801IB (ICH9) LPC Interface Controller (rev 02)
00:1f.2 IDE interface: Intel Corporation 82801IB (ICH9) 2 port SATA IDE Controller (rev 02)
00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 02)
00:1f.5 IDE interface: Intel Corporation 82801I (ICH9 Family) 2 port SATA IDE Controller (rev 02)
01:00.0 VGA compatible controller: nVidia Corporation G92 [GeForce 8800 GS] (rev a2)
02:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8056 PCI-E Gigabit Ethernet Controller (rev 12)
03:00.0 IDE interface: Marvell Technology Group Ltd. 88SE6101/6102 single-port PATA133 interface (rev b2)
05:02.0 Ethernet controller: Marvell Technology Group Ltd. 88w8335 [Libertas] 802.11b/g Wireless (rev 03)
05:03.0 FireWire (IEEE 1394): VIA Technologies, Inc. VT6306/7/8 [Fire II(M)] IEEE 1394 OHCI Controller (rev c0)